Do you typically use distortion plugins as inserts on a track, or as a send on an aux buss? Are they like reverb and delay plugins that way? With the plugins I use, a combination of wet/dry knob and level settings allows me to use them as inserts.

Ditto, I think that's also a good way to think about it. Distortion or EQ (or glitch, filter, or other effects) where you're directly changing or sculpting the core sound, as opposed to influencing the "digital environment" or space around the sound. I think that's a good way for me to think about it, too. I've always just kinda gone by intuition or logic without actively thinking about whether the effect was changing the sound itself, or the space around the sound.